Variable temperature refrigeration



June 4, 1957 T. L. ETHERINGTON 2,794,322

VARIABLE TEMPERATURE REFRIGERATION Filed June 29, 1954 2 Sheets-Sheet 1 inventor Theodore L ftheringion,

y Q/ 4 M His Attorney June 4, 1957 T. L. ETHERINGTON 2,794,322

VARIABLE TEMPERATURE REFRIGERATION Filed June 29, 1954 2 Sheets-heet 2 TA-MPER/ITURE (F) l I l 1 1 1 C 5 so a0 so 5o 40 so no a o :0 20 so so so 10 so so -CH2CIF coMPas/T/o/v (MUL E PERCENT) I PE/FFA UOROPRUPflA/f (c ,7, FfifO/ l .z/(clg OF) .172 van tor I "frigeration system in which a pair 'is plotted against the temperature in United States Patentfi 2,794,322 VARIABLE TEMPERATURE REFRIGERATIGN Theodore L. Etherington, Ballston Lake, N. assignor to General Electric Company, a corporation of New York Application June 29,1954, Serial No. 440,022 Claims. c1. 62-3 This invention relates to refrigeration systems and specifically to a method and apparatus to secure variable temperature levels in such systems.

mixture to match capacity with load over a wide variation in the evaporator temperatures. tem will not match capacity with load unless the load 18 A single refrigerant sysconstant.

Accordingly, it is an object of my invention to provide a new and improved refrigeration system in which a pair of low temperature 'scible refrigerants with different volatility and density characteristics are employed.

It is another object of the invention to provide a refrigeration system which selectively circulates a refrigerant mixture of variable composition in response to the load up on the system.

It is another object of the invention to provide a reof liquid receivers are employed.

It is a further object of the invention'to provide a novel method of refrigeration in which a pair of low temperature immiscible refrigerants are separated and selectively mixed in the refrigeration system to produce variable temperature levels of refrigeration.

In carrying out my invention in one form, a pair of low temperature immiscible refrigerants are selectively mixed and circulated in a refrigeration system to provide variable temperature levels of refrigeration.

These and various other objects, features and advantages of the invention will be better understand from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a schematic view of one form of a refrigeration system which embodies my invention; and

Fig. 2 is a solubility graph determined at the system pressure of aperfluoropropane (C3Fs)and Freon 31 (CHzClF) mixture in which composition in percentage degrees Fahrenheit.

In Fig. l of the drawings, a refrigeration system, which may be used in heat pump construction or in commercial or domestic refrigerators and which is indicated generally at 10, comprises a compressor 11 which communicates on its high pressure side with a condenser 12. Condenser 12 is connected to an operating liquid receiver 13 in which a pair of low temperature immiscible refrigerants 14 and 15 coexist in a mixture 16 to form one liquid phase of desired composition. A storage liquid receiver 17, which contains additional amounts of essentially pure refrigerants 14 and 15 in two separate liquid phases immiscible one with the other, is connected to operating liquid receiver 13 through a tube 18 with a liquid level control valve 19. Tube 18 conveys refrigerant solution 16 from opened to tube 21,

ice

' receiver 13 to receiver 17 for purposes to be explained hereinbelow. A float 20 may be positioned in receiver 17 to actuate valve 19 through a suitable electrical or mechanical connection.

The refrigerant mixture 16 is circulated from the operating receiver 13 to a common tube 21 at the inlet side of an evaporator 22 through an outlet 23, an expansion valve 24, a heat exchanger coil 25 in storage receiver 17, and an outlet 26. Coil 25 carries the low temperature refrigerant mixtures 16 of liquid and vapor,

"which has passed expansion valve 24, to cool the low temperature immiscible refrigerants 14 and 15 inreceiver 17 to approximately the evaporator temperature of the refrigeration system. Expansion valve 24 is shown to be of a conventionaltype which is operated by a valve control 27 which comprises a pressure tube'28 anddiaphragm 29. A temperature-operated or thermostatic valve or sections of capillary tubing may be employed as the expansion device. A three-way, three-position valve 30 controls'a pair of outlets 31 and 32 which are in communcation with refrigerants 14 and 15 in receiver 17. -A load sensing and sequence control device 33 of any conventional construction may be provided to selectively operate valve 30 in response to the system load. Tube 21 connects valve 30 to evaporator 22 which communicates with the low pressure side of compressor 11 to complete the refrigeration system.

The pair of low temperature immiscible refrigerants 14 and 15, which have difierent volatility and density characteristics are selectively mixed and circulated through the refrigeration system in response to the load thereon.

"It is important that each'of the refrigerants which is selected for circulation in the system has a difierentdensity from the other refrigerant and exhibits insolubility in the other refrigerant of the pair at or below customary evaporator temperatures to provide a separation of the refrigerants into two layers in the storage receiver 17. The following pairs of refrigerants, which exhibits different volatilities, solubilities and densities and which possess immiscibility at customary evaporator temperatures, are given as examples of suitable refrigerant combinations to be employed in a variable temperature system: perfluoropropane (CaFs) and methyl chloride (CHgCl), perfluoropropane (CaFs) and Freon 3 1 (CHzClF), pe'rfluorobutane (C-rFm) and Freon 21 (CI-IClaF), perfluorobutane (C4Fl0) and methyl chloride (CHaCl), Freon (CzFaCl) and sulfur dioxide (S02), perfluoropropane (CsFs) and methylbromide (CI-lzrBr), Freon 115 (CzFsCl) and methylene chloride (CHzClz), perfluorobutane (C4F1o) and methylene chloride (CHaClz), and perfluorobutane (C4F10) and ethyl chloride (CzHsCl).

In the operation of the refrigeration system in Fig. 1, the pair of refrigerants 14 and 15, which form a refrigerliquid receiver 13, are selectively mixed and circulated in the system. Three-Way, three-position valve 30 is shown in open position for outlet 31 and tube-21 and in closed position for outlet 32.

Compressor 11 pumps refrigerant m xture 16 through condenser 12 to operating liquid receiver 13. The refrigerant solution is then circulated through outlet 23, expan sion valve 24, coil 25, outlet 26, tube 21, and evaporator 22 to the inlet side of compressor 11. When outlet 31 is refrigerant 14 is added to refrigerant mixture 16 which is circulating in the system. An equal volume of refrigerant mixture 16 is simultaneously conveyed from receiver 13 to receiver 17 through tube 18 and control valve 19. Valve 19 may be actuated by any suitable controls, such as, for example, a float 29, which is positioned in the receiver 17 and connected mechanically or electrically to valve 19. The withdrawal of refrigerant ceiver 17 maintains the temperature therein at evaporator temperature to separate refrigerant mixture 16 into refrigerants 14 and 15 in two immiscible layers.

When the load on the system changes, it activates load sensing and sequence control device 33 to close outlet 31 7 and to open outlet 32 whereby refrigerant 15 is added to refrigerant solution 16 in the same manner as the refrigerant 14. The composition of refrigerant mixture 16 is determined by the system load through a load sensing and sequence control device 33 which operates valve 30 to admit additional essentially pure refrigerant 14 or 15 to the system. The volume of refrigerator mixture 16 remains constant through the simultaneous addition to and Withdrawal from the circulating refrigerant solution. The refrigeration system may circulate either essentially pure refrigerant 14 or 15 or a refrigerant mixture 16 of any desired composition.

In Fig. 2, a solubility graph is shown in which composition in mole percentage of a perfluoropropane (CsFs) and Freon 31 (CHsClF) mixture is plotted against the temperature in degrees Fahrenheit. Such a refrigerant solution is generally miscible above 44 F. and immiscible below this temperature. The temperature of storage receiver 17 in Fig. 1 is maintained at or below the evaporator temperature to maintain the refrigerants 14 and,

15 in two immiscible layers. If the temperature of the refrigerants in the receiver 17 is assumed to be 20 F. for purposes of illustration, one immiscible refrigerant layer is composed of 85.5% by weight of perfluoropropane (CsFa) and 14.5% by weight of Freon 31 (CI-IzClF). The other refrigerant layer is 84% Freon 31 and 16% perfiuoropropane.

As will be apparent to those skilled in the art, the objects of my invention are attained by the use of a pair of low temperature immiscible refrigerants with different characteristics which are selectively mixed and circulated in a refrigeration system to provide variable temperature levels of refrigeration and refrigeration capacities.

While other modifications of this invention and variations of apparatus which may be employed in the scope of the invention have not been described, the invention is intended to include all such as may be embraced within the following claims.

What I claim as new and desireto secure by Letters Patent of the United States is:

1. In a refrigeration system utilizing two low temperature essentially immiscible refrigerants with different volatility and density characteristics, a, compressor, .a condenser, an operating liquid receiver and a storage liquid separate the refrigerants in the storage receiver, means to conduct said refrigerants from the separating means to the inlet of the evaporator, and means to selectively control the relative amounts of said refrigerants to circulate through said evaporator.

2. A method of refrigeration which comprises circulating a refrigerant mixture of a pair of low temperature essentially immiscible refrigerants with different volatility and density characteristics in a refrigeration system, storing a supply of said refrigerants in their immiscible phase in addition to said refrigeration system, increasing the relative amount of one of the refrigerants in said mixture, withdrawing an equal amount of said circulating mixture for return to said storage supply, and cooling said with drawn amount to separate said mixture into two essentially immiscible refrigerants.

3. In a refrigeration system including a compressor, a condenser, and an evaporator, a liquid receiver connected to said condenser and said evaporator, a storage receiver connected to said liquid receiver and said evaporator, a pair of low temperature essentially immiscible refriger ants with different volatility and density characteristics in said storage receiver, means to selectively control the relative amounts of the refrigerants to pass from said storage receiver to said evaporator, and cooling means positioned within said storage receiver to separate the refrigerants.

4. A refrigerant system including an evaporator, a compressor, an operating liquid receiver, and a storage liquid receiver, a pair of low temperature essentially immiscible refrigerants in said storage receiver, a mixture of said refrigerants in said operating receiver, means for circulating said mixture from the said operating receiver through said system, means for maintaining the temperature of the storage receiver as a function of the evaporator temperature, means dependent upon the system load for introducing a quantity of one'of said refrigerants in said storage receiver into the said system, and means for withdrawing an equal quantity of the refrigerant mixture from the said system for return to the said storage receiver.

5. In a refrigeration system including an evaporator, a compressor, a condenser, an operating liquid receiver, and a storage receiver, a pair of low temperature essentially immiscible refrigerants in said storage receiver, means to maintain the temperature of the storage receiver within the immiscible range of the refrigerants therein, a mixture of refrigerants in said operating receiver, means for continuously circulating only a mixture of refrigerants through said system, and means for varying the mixture circulating in said system, said means including introducreceiver, an evaporator, means connecting the outlet of the compressor and the inlet of the condenser, means conecting the outlet of the condenser and the inlet of the said operating liquid receiver, means connecting the outlets of the receivers and the inlet of the evaporator, cooling means connected to the operating liq 'd receiver to ing a quantity of one of the refrigerants in said storage receiver into the system, and simultaneously Withdrawing an equal quantity of the refrigerant mixture from the system and returning the withdrawn quantity to the storage receiver.

References Cited in the tile of this patent UNITED STATES PATENTS 2,277,138 Newton Mar. 28, 1942 2,352,581 Winkler June 27, 1944 2,682,756 Clark 'July 6, 1954 

